Present day aircraft cockpit display systems include navigational maps. These maps may be film strip projected, film strip to video converted, or digitally stored to video converted.
Film strip projected maps feature a standard 35 mm film strip which is viewed directly by the pilot of the aircraft through an optical arrangement. The film strip is mechanically translated and rotated.
Film strip-to-video converted maps feature a standard 35 mm film strip which is illuminated with a small spot of light scanning the film strip with a standard TV raster (flying spot scanner). Light transmitted through the film strip is an instantaneous function of the map image and is converted to video signals. The video signals are used to display the map on a multi-function cockpit display device. An arrangement of this type is advantageous in that it can be located remote from the cockpit. The film strip is mechanically translated and rotation is achieved electronically.
Digitally stored to maps for video conversion feature digitally storing the map in a bulk storage memory rather than optically on a film strip. Digital signals are provided and are converted via a digital to video converter to video signals which are used to display the map on a multi-function cockpit display device. The bulk storage to video arrangement can also be located remote from the cockpit. Map translation is achieved by changing the starting address of the bulk storage memory and map rotation is achieved by electronic rotation of the digital to video converter.
In order to display the map in real time the bulk storage memory is typically downloaded into a refresh memory from which the video signals are provided. An arrangement of this type is advantageous over the film strip arrangements heretofore described in that moving parts are not required.
In prior art digitally stored to maps for video conversion systems the maps are stored element by element in the bulk storage memory. An exorbitant amount of memory is required in order to achieve the same resolution as that achieved with film strip systems. The amount of memory can be reduced by storing only non-redundant digital map data. However, in this event a real time reconstruction arrangement is required.
Accordingly, it is the object of the present invention to provide apparatus and method for real time reconstruction of digital map data for use in association with a digitally stored to video converted map system, whereby the amount of memory required to store the map information is significantly reduced.